Not applicable.
The invention relates to cleaning hard surfaces, particularly metal surfaces, more particularly aluminum and aluminum alloy metal surfaces, still more particularly those that have been initially painted because of their use on the exterior of engines and then heavily soiled by organic deposits during use in engines, so that much or all of the surface to be cleaned has been covered with a tightly adhering carbonaceous deposit at least 0.2 millimeters (hereinafter usually abbreviated as xe2x80x9cmmxe2x80x9d) thick and often, over parts of the surface, more than 1 mm thick. In order to produce an optimal result, all of the carbonaceous deposit and any remaining paint must be completely removed, without excessive attack on the metal surface. In some instances, however, it may be satisfactory to remove at least, with increasing preference in the order given, 50, 75, 85, 95, 97, or 99% of the soil and/or paint. Such cleaning by chemical means is believed to have been practical heretofore only with the aid of cleaning liquids that contain substantial concentrations of organic solvents that are legally defined as Volatile Organic Compounds (xe2x80x9cVOC""sxe2x80x9d) by the U.S. Clean Air Act and related legislation and regulations. Emissions of VOC""s are tightly restricted, so that their use is advantageously omitted or at least reduced as much as possible, consistent with the task to be accomplished. Accordingly, a major object of this invention is to provide a solvent-free, or at least a VOC-free, aqueous liquid process and/or composition, or at least a process and/or composition with a solvent and VOC concentration considerably reduced below currently required levels, that is suitable for cleaning such heavily soiled and usually also painted metal surfaces within a practically useful time. Other alternative and/or concurrent objects are to provide a more economical process, a faster process and/or one requiring less expensive equipment for operation on a large scale, and to reduce hazards of fire and of damage to the environment from discharge of used cleaner. Still other and more detailed objects of the invention will become apparent from the further description below.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description, unless expressly stated to the contrary: percent, xe2x80x9cparts ofxe2x80x9d, and ratio values are by weight or mass; the term xe2x80x9cpolymerxe2x80x9d includes xe2x80x9coligomerxe2x80x9d, xe2x80x9ccopolymerxe2x80x9d, xe2x80x9cterpolymerxe2x80x9d and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; the word xe2x80x9cmolexe2x80x9d means xe2x80x9cgram molexe2x80x9d, and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical, or in fact a stable neutral substance with well defined molecules; the term xe2x80x9cpaintxe2x80x9d and all of its grammatical variations include all materials known by more specialized names such as xe2x80x9clacquerxe2x80x9d, xe2x80x9cvamishxe2x80x9d, xe2x80x9cshellacxe2x80x9d, xe2x80x9cprimerxe2x80x9d, xe2x80x9celectropaintxe2x80x9d, xe2x80x9ctop coatxe2x80x9d, xe2x80x9ccolor coatxe2x80x9d, xe2x80x9cclear coatxe2x80x9d, xe2x80x9cautodeposited coatingsxe2x80x9d, xe2x80x9cradiation curable coatingsxe2x80x9d, xe2x80x9ccross-linkable coatingsxe2x80x9d, and the like and their corresponding grammatical variations; and the terms xe2x80x9csolutionxe2x80x9d, xe2x80x9csolublexe2x80x9d, xe2x80x9chomogeneousxe2x80x9d, and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25xc2x0 C.
The term xe2x80x9caluminumxe2x80x9d when used hereafter in this specification, unless the context requires otherwise, is to be understood to include pure aluminum and all the alloys of aluminum that contain at least, with increasing preference in the order given, 45, 55, 75, or 85% of aluminum by weight.
One major embodiment of the invention is a process for cleaning a metal surface that has on it a carbonaceous soil formed by contact of hot gaseous products of combustion of, or of fuel or lubricant materials for, an internal combustion engine with said metal surface and/or with paint originally present on said metal surface before it was brought into contact with said hot products of combustion of, or fuel or lubricant materials for, an internal combustion engine. The process is particularly suited to, but is not limited to, cleaning metal surfaces that have, during their use before cleaning, formed external surfaces of an internal combustion engine. This cleaning process most preferably results in a surface completely cleaned of the carbonaceous soil formed as described above and of any paint originally present on the surface. A process according to the invention includes an operation of contacting the surface to be cleaned with an aqueous liquid cleaning composition that comprises, preferably consists essentially of, or more preferably consists of, water and the following components:
(A) a component of inorganic alkalinizing agents; and
(B) a component of surfactant molecules that are not inorganic alkalinizing agents, at least part of said surfactant molecules being nonionic surfactants; and, optionally, one or more of the following dissolved, stably dispersed, or both dissolved and stably dispersed components:
(C) a component of hydrotroping agent that is not part of any of immediately previously recited components (A) and (B);
(D) a component of corrosion inhibitor that is not part of any of the previously recited components (A) through (C);
(E) a component of sequestering agent that is not part of any of the previously recited components (A) through (D);
(F) a component of coloring agent that is not part of any of the previously recited components (A) through (E);
(G) a component of preservative material that is not part of any of the previously recited components (A) through (F); and
(H) a component of organic solvent that is not more than 20% of the total composition.
In this description, xe2x80x9cstably dispersedxe2x80x9d means that the component so described can be dispersed by mixing, within 1 hour of its introduction into the liquid phase in which the component in question is described as stably dispersed, to produce a liquid mixture which has only one bulk phase detectable with unaided normal human vision and does not spontaneously develop any separate bulk phase detectable with normal unaided human vision within 24 hours, or preferably, with increasing preference in the order given, within 7, 30, 60, 90,120, 180, 240, 300, or 360 days, of storage without mechanical agitation at 25xc2x0 C. after being initially mixed. (The word xe2x80x9cbulkxe2x80x9d in the preceding sentence means that, to be considered as a bulk phase, a phase must occupy at least one volume of space that is sufficiently large to be visible with unaided normal human vision and is separated from at least one other phase present in the dispersion by a boundary surface that can be observed with unaided normal human vision. Therefore, a change of the composition from dear to hazy or from hazy to clear does not indicate instability of a dispersion within this definition, unless a separate liquid or solid phase develops in the mixture in at least one volume large enough to see independently with unaided normal human vision.) Also in this description, xe2x80x9calkali stablexe2x80x9d when referring to a surfactant means that the surfactant is capable of coexisting at its critical micelle concentration in an aqueous solution also containing at least, with increasing preference in the order given, 5, 10, 15, 20, 25, or 29% of sodium hydroxide, without any chemical reaction (except possibly for reversible neutralization) between the surfactant and the sodium hydroxide and without the formation of any separate bulk phase detectable with normal unaided human vision within 24 hours, or preferably, with increasing preference in the order given, within 7, 30, 60, 90, 120, 180, 240, 300, or 360 days, of storage without mechanical agitation at 25xc2x0 C. after being initially mixed. xe2x80x9cOrganic solventxe2x80x9d as used in defining component (H) above means any organic compound or homogeneous mixture of organic compounds that is a liquid at 25xc2x0 C. and normal atmospheric pressure.
Process embodiments of the invention may include other process operations, particularly those which are conventional in themselves following cleaning in the prior art. In particular, after the completion of one or more operations of chemical cleaning using a working composition according to this invention as described above, it is very often advantageous to use a spray of water with substantial impingement force, such as is provided by a power washer or spray wand, as a rinse after the chemical treatment. The mechanical action provided by such a rinse is often useful in removing the last traces of soil and/or paint from the surface to be cleaned.
A second major embodiment of the invention is a composition that is particularly advantageously used in a metal cleaning process. The working and concentrate metal cleaning compositions of the invention comprise, preferably consist essentially of, or more preferably consist of, water and the following dissolved, stably dispersed, or both dissolved and stably dispersed components:
(Axe2x80x2) a component of inorganic salts of weak acids and strong alkalis, said salts including at least one silicate and at least one phosphate;
(Bxe2x80x2) a component of alkali stable nonionic surfactant molecules that are not part of immediately previously recited component (A); and
(Cxe2x80x2) a component of hydrotroping agent molecules that are not part of either of immediately previously recited components (A) and (B); and, optionally, one or more of the following components:
(Dxe2x80x2) a component of corrosion inhibitors that are not part of any of the previously recited components (A) through (C);
(Exe2x80x2) a component of sequestering agents that are not part of any of the previously recited components (A) through (D);
(Fxe2x80x2) a component of coloring agent that is not part of any of the previously recited components (A) through (E);
(Gxe2x80x2) a component of preservative material that is not part of any of the previously recited components (A) through (F); and
(Hxe2x80x2) a component of organic solvent that is not more than 20% of the total composition.
In this description, xe2x80x9cstably dispersedxe2x80x9d, xe2x80x9calkali stablexe2x80x9d, and xe2x80x9corganic solventxe2x80x9d have the same meanings as for the description of the major process embodiment of the invention already described above.
Compositional embodiments of the invention include liquid compositions ready for use as such in cleaning (i.e., xe2x80x9cworking compositionsxe2x80x9d) and concentrates suitable for preparing working compositions by dilution with water. Concentrates may be single package or multiple, usually dual, package in nature. A multiple package type of concentrate is preferred when not all of the ingredients desired in the working composition are sufficiently soluble or stably dispersible at the higher concentrations required for a one package concentrate composition, which is otherwise preferred. For example, at some concentrations, sometimes preferred polymeric organic sequestering agents and some preferred alkalinizing components can not be jointly solubilized. The two components are then placed in separate packages with other portions of the formulation so that stable solutions or dispersions can be formed after mixing and dilution. A two package concentrate system has some advantages in that the two components can be mixed in different proportions to provide more effective cleaning for particular soils, soil combinations, and/or types of substrate to be cleaned. Ordinarily, however, at least for users for whom cleaning requirements do not vary greatly, single package concentrates are preferred because they are more convenient.
Compositions of the present invention are particularly useful for cleaning in a process according to the invention as described above but are also useful for cleaning any metallic and/or non-metallic hard surfaces such as ceramics and plastics when such surfaces are heavily soiled.